Conventional silicon semiconductor and thin layer field effect transistor (TFT) using a compound semiconductor are used not only in ordinary integrated circuits but also in widening range of applications. In particular, use of TFT in liquid crystal display is quite common, and with the recent increase in the size and definition of the liquid crystal display, an increasing number of TFT are used in the display corresponding to the increased number of the pixel.
However, in the case of conventional metal semiconductors that had been used, slight defects were inevitably formed on the TFT during the process of the patterning by photoresist or the like and the etching in the course of forming the circuit on the substrate. In addition, the production cost could be reduced only to a certain degree in the case of the TFT produced by such process. Other thin displays such as plasma display and organic EL display suffered from the same situation as long as they used the TFT.
The recent trend of the increased area and definition of the display naturally results in the increased incidence of the defects in the TFT product, and there is a strong demand for a method which is capable of minimizing the TFT defects.
In addition, the need for the process of the patterning by photoresist and the etching limited the reduction of the production cost.
On the other hand, there are widening new applications for the silicon semiconductor having the MIS (metal/insulator/semiconductor) structure and the TFT using the compound semiconductor, and further reduction in the price and flexibility of the device have been requested. Exemplary such applications include IC tag, flexible display, printable integrated circuit, and electronic paper, and in order to correspond to these new applications, use of organic insulator and organic semiconductor has been attempted since such organic materials can be produced at a reduced cost, and they have various functional properties such as flexibility enabling their use for various type of device. However, not much is known for the organic insulator material. For example, JP-A 5-508745 describes that a device prepared by using an insulator organic polymer having a relative dielectric constant of at least 5 for the insulator layer and a polycondugated organic compound having a weight average molecular weight of up to 2,000 for the a semiconductor layer has the field effect and a mobility of about 10−2 cm2V−1s−1. However, α-sexithienyl is used for the organic semiconductor material and formation of the semiconductor layer by vapor deposition is required, and the process of the patterning by photoresist and the etching is still required, and this makes the cost reduction difficult.